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Maintaining Connected Coverage for Wireless Sensor Networks. Jehn-Ruey Jiang and Tzu-Ming Sung Department of Computer Science and Information Engineering, National Central University, Taiwan. The 28th I nternational C onference on D istributed C omputing S ystems Workshops ICDCS 2008.
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Maintaining Connected Coverage for Wireless Sensor Networks Jehn-Ruey Jiang and Tzu-Ming Sung Department of Computer Science and Information Engineering, National Central University, Taiwan The 28th International Conference on Distributed Computing Systems Workshops ICDCS 2008
Outline • Introduction • Problem Formulation • The Density Control Algorithm • Simulation Results • Conclusion
Introduction • The wireless sensor network consists of a large number of micro sensors for different application • Battlefield surveillance • Environment monitoring • Animal tracking • The most of the sensors are • supported battery • distributed over a large area • It is hard to recharge
Introduction • How to extend the network lifetime is an important problem in WSNs. • To deploy high density sensors • To use power saving mechanism
Problem Formulation • Sensors • Asynchronous • Position-less • Density-high • Sensing range • Rs • Communication range • Rc • Rc ≥ 2Rs The interesting area G
Problem Formulation • In the high density sensor deployment • How to connect the coverage with the least umber of the sensor? • To power saving in the asynchronous system • How to provide a mechanism for sensor to aware of active sensors’ statuses by asynchronously beaconing
The Optimal (Least) Number of Sensors • R. Kershner, “The Number of Circles Covering a Set”,American Journal of Mathematics
R The Density Control Algorithm • Two type of the beacon • a beacon :near beacon 1/ <α<1 • b beacon :far beacon
The Density Control Algorithm • The power saving in asynchronous system • Monitor interval • Beacon window • TI (traffic indication) window • n beacon intervals • Non-monitor interval • Beacon window • TI (traffic indication) window round
The Density Control Algorithm • j node can receive the beacon and store to the two type set • A set • j can hear i’s a-beacon • i is older than j • i is oldest among those whose • AB set • J can hear I’s b-beacon but not hear a-beacon
The Density Control Algorithm In the beacon interval the sensor will broadcast the beacon with the vector(time, root, level) (158,a,0) (143,b,0) (158,a,-1) (158,a,-2)
Simulation Results • Language C • Area : 100m x 100m • Rc =20 meters • Rs = 10 meters • Beacon interval 100ms • α= 0.7, 0.75, 0.8 and 0.85
Simulation Results Optimal hexagon-base deployment : 42 sensors The Algorithm : 51 sensors The cover factor R = 51/42 = 1.21
Conclusion • Under the assumption Rc ≥ 2Rs • This paper propose the algorithm • Without location information • Use two type beacons • Near beacon • Far beacon • To approximate the optimal connected hexagonal deployment